Linear actuation cables are used in many applications to transmit push/pull motion between mechanical components. These cables consist of a hollow outer sheath or conduit which surrounds an axially movable inner core wire. When both ends of the conduit are anchored to a fixed structure, a push or pull motion applied to one end of the core wire will be transmitted to the other end. The linear actuation cable will function properly even if it is very long or follows an extremely convoluted path, as long as the ends of the conduit are securely anchored in their proper positions.
End fittings have been used to anchor the conduit ends in their operative positions. Typically, such an end fitting is made of plastic and is generally tubular in shape with one end receiving and securely holding the conduit so that the core wire extends through the inside of the fitting and out the other end. A common way to anchor the end fitting in the desired installed position on the supporting structure is to provide it with a deformable detent means which interacts with a corresponding detent means on the structure. When the end fitting is placed in contact with the structure and moved toward the installed position, interference between the detent means and the structure causes the detent means to bend away from its at-rest position. When the fitting fully reaches the installed position, its detent means comes into cooperating alignment with the detent means on the structure and snaps into locking engagement therewith. If the end fitting is not pushed far enough to attain the installed position, the detent means will not snap into locking engagement with the structure, and the fitting will only be maintained in contact with the structure by friction. Consequently, the end fitting may work itself loose from the structure due to vibration during use.
In a production line environment, it is possible that the person installing the cable will not properly position the end fitting so as to achieve its locked relationship with the structure. This improper installation will not be readily apparent to a quality control inspector since there may be only a small fraction of an inch difference between the locked and unlocked positions. The lack of a distinct visual difference between the locked and unlocked positions results in a significant number of improperly installed, i.e., not lockingly engaged, end fittings going undetected, with the subsequent likelihood that the end fitting will come loose from the structure causing the linear actuation mechanism to function improperly.